Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in the United States, Australia or elsewhere.
Centrifugal separators are often used for the separation of solids and liquids from slurry. For example, U.S. Pat. No. 6,109,453 and US Patent Application Publication No. 2014/0217008 A1 show such separators. Such separators are used e.g. for separating coal solids from a coal slurry that includes water. These centrifuges typically have an inlet where slurry is deposited and then conveyed to a rotational basket. The slurry next traverses the rotational basket, with the liquids being expelled outwards through the basket and the solids being carried down tapered sides of the basket. When solids reach an outermost edge of the basket, the solids leave the outermost edge of the basket at speed and strike the walls of an outlet region of the centrifuge. The solids are then channelled by the walls of the outlet region to an outlet chute.
Coarse coal centrifuges, such as the FLSmidth VM series, incorporate an opening in the back wall of the separation housing to allow the drive shaft and flange to pass through into the effluent portion. This opening often results in material (e.g. water and fine solids) passing into the drive portion of the centrifuge leading to maintenance difficulties, accelerated corrosion and accelerated wear of the critical drive components that govern the operation of the machine. US Patent Application Publication No. 2014/0217008 A1 discloses a rubber seal between the separation housing and the bearing housing. However, such a seal is inefficient. While that seal prevents material inside the separation housing from leaking out of the centrifuge, it does not prevent material from inside the separation housing from leaking into the drive portion of the centrifuge.
A solution for reducing the amount of or eliminating completely, material and liquid contamination around and into the drive portion is needed to ensure longevity and to reduce the risk of premature failure of drive components. However, as machine cost is a critical concern for most clients when purchasing a centrifuge it is necessary that the solution is inexpensive to manufacture and quick to install. Because the system is also exposed to water, air and fine particle abrasion such a solution will also need to be able to withstand the foregoing elements.
Coarse coal centrifuges also require some means of restricting material from passing out of the product discharge outlet back into the effluent portion is after separation and some means of restricting liquid from leaking out of the effluent portion to the product discharge outlet after separation. Traditionally, as is the case for FLSmidth's VM centrifuge and as shown in FIG. 9, this is achieved through the use of close running clearances between the basket and the separation housing. However, such an approach is costly and inefficient.
In order to reduce the cost (introduced by the requirement for machining of the separation housing and basket to achieve close running clearances) and to improve the separation between the material and liquid in the product discharge outlet an improved sealing arrangement is required.